The present invention relates to a method and a composition for identifying diverse products that can be made of diverse materials, such as paper documents, appliances, clothing, boxes, glass products, plastic finish products and others in a covert manner.
It is, of course, well known that various means have been proposed in the past for covertly marking and identifying items. The previously used identifying methods utilized essentially the so-called ultraviolet inks or paints that fluoresce when subjected to an ultraviolet light source. Such simple fluorescent markings used in conjunction with ultraviolet lights provide of course a dramatic effect, since the marking, which is originally seemingly invisible in visible or normal light, becomes brightly florescent under ultraviolet radiation. However, the fundamental drawback of such systems is that they are by their nature readily visible upon illumination by ultraviolet radiation and, therefore, can be easily located by any counterfeiter or product diverter. Consequently, such marks can be removed or they can be altered, since fluorescent dyes known as optical brighteners and inks are readily available today on the market.